1. Field of the Invention
The present invention relates to an electronic unit such as a voltage-controlled oscillator for use in a mobile phone.
2. Description of the Related Art
A conventional electronic unit such as a voltage-controlled oscillator will be described with reference to FIGS. 9 through 12. FIG. 9 is a plan view, FIG. 10 is a front view, FIG. 11 is a side view, and 12 is a bottom view. A rectangular circuit board 21 is formed by stacking together a plurality of substrates. As indicated by the shaded portions in FIG. 9, wiring patterns 22 and grounding patterns 23 are formed on an upper surface 21a of the circuit board. Although not shown, the wiring patterns 22 and the grounding patterns 23 are also formed between the layers of the board.
A plurality of side through portions 21c consisting of arcuate recesses are formed on the four side surfaces 21b of the circuit board 21. The side through portions 21c are equipped with side electrode portions 24 connected to the wiring patterns 22 and side electrode portions 25 connected to the grounding patterns 23.
A plurality of wiring terminal electrode portions 26 and grounding terminal electrode portions 27 are provided at predetermined intervals on the lower side 21d of the circuit board 21. The wiring terminal electrode portions 26 are connected to the side electrode portions 24, which are connected to the wiring patterns 22, and the grounding terminal electrode portions 27 are connected to the side electrode portions 25, which are connected to the grounding patterns 23.
A box-shaped cover 28 formed of a metal plate has a top wall 28a and side walls 28b which are formed by downwardly bending the four side portions of the top wall 28a and whose lower portions are open. Although not shown, various electronic parts are arranged on the upper surface 21a of the circuit board 21, and the cover 28 is mounted to the circuit board 21 so as to cover these electronic parts.
The cover 28 is arranged on the circuit board 21 such that the side walls 28b are positioned on the inner side of the circuit board 21, avoiding the side through portions 21c, which are recesses. Thus, a large extra space S2 exists between the end portions of the circuit board 21 and the side walls 28b of the cover 28 at the periphery of the circuit board 21. The cover 28 is mounted to the circuit board 21 by soldering the side walls 28b to the grounding patterns 23.
The conventional electronic unit, constructed as described above, is surface mounted on the mother printed board (not shown) of, for example, a mobile phone, by soldering, with the wiring terminal electrode portions 26 and the grounding terminal electrode portions being placed on the mother printed board.
In the conventional electronic unit, the side electrode portions 24 and 25 are formed in the side through portions 21c consisting of recesses provided in the side surfaces 21b of the circuit board 21, and the patterns 22 and 23 on the upper and lower surfaces of the circuit board 21 are connected to the terminal electrode portions 26 and 27 by means of the side electrode portions 24 and 25, so that the cover 28 is arranged so as to avoid the side through portions 21c. Thus, a large extra space S2 exists in the periphery of the circuit board 21, between the end portions of the circuit board 21 and the side walls 28b of the cover 28, such that the size of the circuit board 21 is rather large. This means that it is impossible to effectively utilize the entire upper surface 21a of the circuit board 21 as the wiring patterns 22 and thus, this conventional electronic unit is not suitable for use in a mobile phone, which requires both size and weight reductions.
Accordingly, it is an object of the present invention to provide an electronic unit having both size and weight reductions.
To achieve the above object, there is provided, in a first aspect of the present invention, an electronic unit comprising a circuit board having on its upper surface a wiring pattern and a grounding pattern, an electric part arranged on the circuit board, and a cover mounted to the circuit board so as to cover the electric part. On the lower surface of the circuit board there are provided a wiring terminal electrode portion and a grounding terminal electrode portion. Connection conductors provided in respective through-holes provide connections between the wiring pattern and the wiring terminal electrode portion and between the grounding pattern and the grounding terminal electrode portion.
In a second aspect of the present invention, an electronic unit is provided wherein a recess, extending over at least the side surface and the lower surface of the circuit board, is formed at positions corresponding to the wiring terminal electrode portion and the grounding terminal electrode portion.
In a third aspect of the present invention, an electronic unit is provided wherein a cutout portion is formed by cutting a corner portion of the rectangular circuit board at a position corresponding to the wiring terminal electrode portion or the grounding terminal electrode portion.